Hi all,
Just picked up an LMT buffer kit for a 300BLK build I’m working on. The rifle will have a 10.5" barrel and will be run mostly suppressed. I was wondering since the LMT buffer kit comes with what I believe is an H buffer (3 OZ buffer) if that will suffice or should I be using an H2 buffer? The buffer is said to be a carbine buffer. Thanks.
The buffer weight you describe is a Carbine buffer, the lightest standard weight.
You may get more direct advice on this in the alternative calibers forum.
However, my guess is that a Carbine buffer will be too light for a 300BLK suppressed.
For 5.56, an H1 or H2 buffer is going to be standard before suppression. Suppressing adds to pressure and typically benefit will be seen with a heavier buffer. I’d start with an H2 or (possibly) H3 buffer if you are going to run mostly suppressed. Not sure the barrel provenance, but if it is gassed appropriately, you may want to keep the Carbine buffer for use without a suppressors. Too many variables between barrels, especially with 300BLK, to give an answer without your trying it first.
Thats what I suspected. I figured I may need an H2. I should’ve realized that before ordering the kit. I suppose I can always sell the standard buffer since its LMT. Thank you.
Do you have a standard AR or plan to build another lower?
If so, order an MWS receiver extension kit, save the receiver extension (compatible with A5 buffers) for your next build, and use the included H3 buffer in the lower you are currently building.
No I don’t unfortunately. It is what it is. I could always just keep it in case I’m experiencing cycling issues in the future.
With 300BLK, the biggest variable is supersonic or subsonic ammo.
It depends on the exact barrel, but generally you’ll want the lighter buffer for subsonics and the heavier buffer for supersonics.
BCM used to advise H3’s with their 300 Blk’s.
That’s what I run and I shoot Barnes Black Tip (110 gr) about exclusively
So it sounds like I’ll probably need both buffers anyway. I shoot whatever I can get my hands on (except steel case) suppressed.
I can get my hands on a H3 easier than I can an H2. I’ll probably grab one.
I use h3-H4 for my 9” and 8.3” always suppressed. With your longer barrel I suspect the H3 would be good. But I would test with an H2 if firing supers without a can. Not sure a single buffer weight is optimal for all weight bullets with and without a can.
Correction: My 8.3 has an A5 tube with H3 buffer. Carbine tube with H3 on the 9”.
I ran a Spikes ST2 buffer (whatever they consider that) in my 8.3" build when I ran it suppressed with no issues. I used a mixture of rounds with that. I never shot it unsuppressed. I’m assuming that is the equivalent of an H2?
Does the powdered tungsten make an ST-2 perform like the heavier H2? I have no idea.
If it helps I looked it up, the T2 is 4 Oz.
Almost all of this is going to depend on how gassy the barrel is along with the level of back pressure from your can. And as a warning, the majority of barrel makers are completely confused about how big the gas port for 300 blk should be.
Although I don’t like the JP Silent Capture systems for 556 guns I think it can be super helpful with 300 blk. The recipe that we have found to work the best is an SLR adjustable gas block along with a JP heavy SCS. With the gun suppressed adjust the gas with subs to lock back and then give it one or two more clicks. From there you should be good to go with both subs and supers. If you are just shooting supers (no idea why you would do this) just use an H3 or an A5 system with a green springco and A5H2.
This first paragraph is completely true.
Part of the utility and beauty of 300BLK is that it can run well in all 4 modes without an adjustable gas system.
This of course requires the barrel to be configured and ported properly, but it is certainly possible.
I called LMT they say they use their standard carbine buffer in all their platforms. He said to just run it with the carbine buffer first and if I’m not happy with how it cycles or recoils then to go up to an H buffer but he believes the H2 would even be too heavy and could cause cycling issues.
.300blk can be a fickle mistress. You have four different combos to account for: suppressed supers, suppressed subs, unsuppressed supers, and unsuppressed subs. Then you have to figure out how many of those combos you want to run. Once that’s settled, it’s typically recommended to run the heaviest buffer you can that’ll reliably lock back on the lowest backpressure combo you intend to use.
I know my 8.3" BA Hanson barrel with a SiCo Omega has a ton of backpressure. I used a BRT EZ tune gas tube to tame it a bit, but it’ll still reliably cycle and lock back using suppressed subs with an A5H4 and Sprinco green, so that’s what I run.
Everything depends on the loads you use and the size of the gas port in the barrel. Shoot it with the ammo you plan to use then change the buffer to tune the rifle to your liking.
I tried both an H3 and H4 in my 9.75” PWS running an AAC Tirant 45 can and found no discernible difference using various bullet weights, all subsonic.
Before anyone comments, yes, it’s not the ideal can. It’s a boredom build that exists only because I had that stupid can lying around without a host.
I’ll give the carbine buffer a shot once I’m done with this build. I’ll be running my Surefire SOCOM 7.62 mini 2 can on this.